Capacitive sensor for monitoring gas concentration

ABSTRACT

Embodiments disclosed herein include gas concentration sensors, and methods of using such gas concentration sensors. In an embodiment, a gas concentration sensor comprises a first electrode. In an embodiment the first electrode comprises first fingers. In an embodiment, the gas concentration sensor further comprises a second electrode. In an embodiment, the second electrode comprises second fingers that are interdigitated with the first fingers.

BACKGROUND 1) Field

Embodiments of the present disclosure pertain to the field ofsemiconductor processing and, in particular, to capacitive gasconcentration sensors.

2) Description of Related Art

As semiconductor manufacturing continues to scale to smaller and smallercritical dimension (CD) and feature sizes, it becomes more important toprecisely control chamber processing conditions. One such chambercondition is the concentration of gasses that are flown into thechamber. Currently, mass flow meters and valves are used to set the flowof gasses into the chamber. However, such devices do not provide thenecessary resolution for advanced nano-scale device high volumemanufacturing process. The direct monitor and control of the gasconcentrations is critical and necessary.

In some instances laser sensors have been used to provide more accuratecontrol of gas concentration into chambers. Laser sensors have been usedin research settings. However, laser sensors are complicated anddifficult to integrate into the processing tool. As such, laser sensorsare not cost effective, and are exceedingly difficult to integrate intotools used for high volume manufacturing (HVM) environments.

SUMMARY

Embodiments disclosed herein include gas concentration sensors, andmethods of using such gas concentration sensors. In an embodiment, a gasconcentration sensor comprises a first electrode. In an embodiment thefirst electrode comprises first fingers. In an embodiment, the gasconcentration sensor further comprises a second electrode. In anembodiment, the second electrode comprises second fingers that areinterdigitated with the first fingers.

Embodiments disclosed herein may also comprise a semiconductorprocessing tool. In an embodiment, the semiconductor processing toolcomprises a chamber, a gas line for providing a source gas to thechamber, and a gas concentration sensor in the gas line. In anembodiment, the gas concentration sensor comprises a first electrode,where the first electrode comprises first fingers. In an embodiment, thegas concentration sensor further comprises a second electrode, where thesecond electrode comprises second fingers that are interdigitated withthe first fingers.

Embodiments disclosed herein may also comprise a gas feed architecturethat comprises a first gas line, where the first gas line receives afirst gas from a first gas source. In an embodiment an ampule is alongthe first gas line, and the ampule supplies a second gas to the firstgas line. In an embodiment, a first gas concentration sensor is afterthe ampule. In an embodiment, the first gas concentration sensorcomprises a first electrode, where the first electrode comprises firstfingers, and a second electrode, where the second electrode comprisessecond fingers that are interdigitated with the first fingers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional illustration of a capacitive sensor, inaccordance with an embodiment.

FIG. 2A is a plan view illustration of a capacitive sensor, inaccordance with an embodiment.

FIG. 2B is a cross-sectional illustration of the capacitive sensor inFIG. 2A, in accordance with an embodiment.

FIG. 3A is a graph of the capacitance per unit length and the fielddecay length, in accordance with an embodiment.

FIG. 3B is a graph illustrating the variance in pressure and theresulting capacitances read by a capacitive sensor, in accordance withan embodiment.

FIG. 3C is a graph illustrating the variance in temperature and theresulting capacitances read by a capacitive sensor, in accordance withan embodiment.

FIG. 3D is a graph illustrating the sensitivity of the capacitor sensor,in accordance with an embodiment.

FIG. 3E is a graph illustrating the sensitivity of the capacitor sensor,in accordance with an additional embodiment.

FIG. 4A is a perspective view illustration of a capacitive sensor thatis raised up from the substrate by spacers, in accordance with anembodiment.

FIG. 4B is a perspective view illustration of a capacitive sensor formedon a flexible substrate that is formed into a shell, in accordance withan embodiment.

FIG. 4C is a perspective view illustration of a capacitive sensor withplate like fingers that are interdigitated, in accordance with anembodiment.

FIG. 4D is a perspective view illustration of a capacitive sensor withpin like fingers that are interdigitated, in accordance with anembodiment.

FIG. 5A is a schematic of a gas feed architecture with a pair ofcapacitive sensors for measuring gas concentration, in accordance withan embodiment.

FIG. 5B is a schematic of a gas feed architecture with a first gas line,a second gas line, and a third gas line, and capacitive sensors in thefirst gas line and the second gas line, in accordance with anembodiment.

FIG. 6A is a cross-sectional illustration of a sensor system with a gasconcentration sensor, a temperature sensor, and a pressure sensor thatare integrated on one substrate or module with a processor , inaccordance with an embodiment.

FIG. 6B is a cross-sectional illustration of a sensor system with a gasconcentration sensor, a temperature sensor, and a pressure sensor thatare coupled to a processor by an interconnect, in accordance with anembodiment.

FIG. 7 is a cross-sectional illustration of a semiconductor processingtool with a capacitive gas concentration sensor, in accordance with anembodiment.

FIG. 8 illustrates a block diagram of an exemplary computer system, inaccordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

Capacitive gas concentration sensors are described herein. In thefollowing description, numerous specific details are set forth in orderto provide a thorough understanding of embodiments of the presentdisclosure. It will be apparent to one skilled in the art thatembodiments of the present disclosure may be practiced without thesespecific details. In other instances, well-known aspects, such asintegrated circuit fabrication, sensor fabrication, sensor modulepackaging/integration, are not described in detail in order to notunnecessarily obscure embodiments of the present disclosure.Furthermore, it is to be understood that the various embodiments shownin the Figures are illustrative representations and are not necessarilydrawn to scale.

As noted above, advanced semiconductor processing requires precisecontrol of processing parameters, such as gas concentrations in gassesflown into the processing chamber. In order to allow for precise (e.g,the resolution can be as low as a few ppm) gas concentrationmeasurements in high volume manufacturing environments, the gasconcentration sensor needs to be simple, low cost, and easily integratedinto the processing environment.

Accordingly, embodiments disclosed herein include capacitive sensorarchitectures for determining gas concentrations. In an embodiment, thecapacitive sensors are easily integrated into the gas lines ofsemiconductor processing tools. Furthermore, embodiments disclosedherein include capacitive sensor architectures that are able to detectparts per million (PPM) concentrations. Accordingly, incredibly highprecision of the gas concentrations flown into the chamber can beobtained. Additionally, through integration of multiple capacitivesensors and gas feed architectures, even greater precision of the gasconcentrations can be obtained.

Referring now to FIG. 1, a cross-sectional illustration of a portion ofa capacitive sensor 100 is shown, in accordance with an embodiment. Inan embodiment, the capacitive sensor 100 is provided on a substrate 101.The capacitive sensor 100 may comprise a first electrode 110 _(A) and asecond electrode 110 _(B). Capacitances can be read between the firstelectrode 110 _(A) and the second electrode 110 _(B). A firstcapacitance C_(S) is provided through the substrate 101, and a secondcapacitance C_(E) is provided external to the substrate 101. The firstcapacitance C_(S) is dependent on the composition of the substrate 101and the temperature of the substrate 101. In contrast, the secondcapacitance C_(E) will change depending on the concentrations, pressure,temperature, etc. of the gasses that flow over the first electrode 110_(A) and the second electrode 110 _(B).

In an embodiment, the capacitance can be used to measure the gasconcentration using Equation 1. ε_(r) is the dielectric constant of thegas, N is the gas density (i.e., gas concentration), α_(e) is thepolarizability of gas molecules, and ε₀ is the vacuum permittivity.ε_(r) can be derived from the measured capacitance.

ε_(r)=1+Nα _(e)/ε₀   Equation 1

Referring now to FIG. 2A, a plan view illustration of a sensor 200 isshown, in accordance with an embodiment. The capacitor is made of thefirst electrode 210 _(A) and the second electrode 210 _(B) that may havefingers 214 _(A) and 214 _(B), respectively. The fingers 214 _(A) and214 _(B) may extend away from lines 212 _(A) and 212 _(B), respectively,to scale up the capacitance. In an embodiment, the fingers 214 _(A) and214 _(B) are interdigitated as pairs in order to provide an increase inthe capacitance between the first electrode 210 _(A) and the secondelectrode 210 _(B) by increasing the numbers of electrode pairs. So byscaling the length of fingers 214 a and 214 _(B) as well as increasingthe number of pairs of fingers a proper design can be implemented toachieve high sensitivity.

Referring now to FIG. 2B, a cross-sectional illustration of the sensor200 across the dashed line in FIG. 2A is shown, in accordance with anembodiment. As shown, the fingers 214 _(A) and 214 _(B) over substrate201 have a width W and are separated from each other by a distance d.The width W and distance d can be modulated in order to provide goodsensitivity.

Referring now to FIG. 3A, a graph of the capacitance per finger per unitlength (left side) and the field decay length (right side) is shown, inaccordance with an embodiment. As shown, the capacitance depends on therelative dimensions (W/(W+d)). As the distance d is reduced, thecapacitance increases and provides more sensitivity to the sensor.However, increases in capacitance result in a decrease in the field,which means the field is confined near the surface area. Having a largerfield distribution or penetration allows for more gas above the sensorto be sensed. Accordingly, a balance between field decay length or fieldpenetration to the gas volume and total capacitance may need to bechosen. In a particular embodiment, W/(W+d) may be chosen to beapproximately 0.5.

Referring now to FIG. 3B and 3C graphs depicting capacitance relative togas concentration for different parameters are shown, in accordance withan embodiment. In FIGS. 3B and 3C, the fingers are assumed to have aW/(W+d) value of 0.5, and the capacitance through the substrate isignored. The gas concentration of TDMAT in argon between 0% TDMAT and100% TDMAT is used as an example. As shown in FIG. 3B, increases in thepressure leads to higher capacitances, and as such, highersensitivities. In some embodiments, a pressure sensor may be coupledwith the capacitive gas concentration sensor in order to compensate forpressure variations that may be provided in the readings. As shown inFIG. 3C, lower temperatures lead to increases in capacitance, and assuch, higher sensitivities. In some embodiments, a temperature sensormay be coupled with the capacitive gas concentration sensor in order tocompensate for thermal noise that may be provided in the readings.

Embodiments disclosed herein allow for high sensitivity. As shown inFIG. 3D, concentration variations down to 1%-3% can be determineddepending on the operation pressure. The sensor configuration used tomodel the sensitivities in FIG. 3D is a W/(W+d) of 0.5, with 1,000 pairsof fingers with a 1mm finger length, and an overall sensor dimension of2 mm×10.5 mm. Additional sensitivity can be obtained by scaling up thesize of the sensor. For example, with a finger length of 10 mm, 2,000pairs of fingers, and an overall sensor dimension of 10 mm×10 mmimproved sensitivity to be at or less than ppm concentration can beobtained, as shown in FIG. 3E. For example, for the detection of 1%variation over 0.1% relative concentration, it would need thesensitivity of the sensor in the range of 10 ppm.

Referring now to FIG. 4A a perspective view illustration of a capacitivesensor 400 is shown, in accordance with an embodiment. As shown, thecapacitive sensor 400 comprises a first electrode 410 _(A) and a secondelectrode 410 _(B). In an embodiment, each electrode 410 _(A) and 410_(B) may comprise conductive lines 412 _(A) and 412 _(B) with fingers414 _(A) and 414 _(B) extending away from the conductive lines 412 _(A)and 412 _(B). The fingers 414 _(A) may be interdigitated with thefingers 414 _(B).

In an embodiment, the conductive lines 412 _(A) and 412 _(B) may beraised up off or floated from the substrate surface (not shown) . Bymoving the conductive lines 412 _(A) and 412 _(E) off of the substrate,the gas that is being detected may flow both above and below the fingers414. As such, the capacitance contributed from the substrate is avoidedand a higher portion of the measured capacitance is attributable to theconcentration of gasses flowing over the sensor 400. Furthermore thefloated electrode designs can minimize the parasitic effects (e.g,thermal noise from the substrates) to improve signal noise ratio (SNR).Higher capacitances can be used to improve the sensitivity of the sensor400. In a particular embodiment, raising the fingers 414 off of thesubstrate may allow for a doubling of the sensitivity of the sensor 400.If the sensor 400 was on the substrate, it may be difficult to determineif a change in capacitance was the result of a change in gasconcentration or a change in the temperature of the substrate. In anembodiment, the capacitance of the sensor 400 may be determined byapplying a DC or AC signal to the fingers 414. However, it is to beappreciated that other signaling regimes may also be used to extract thecapacitance value. For example, a spectrum of the sensor with otherpassive or active elements in the module can be used to extract aresonance frequency signal that may be used to measure the capacitanceof the sensor 400 in some embodiments.

Referring now to FIG. 4B, a perspective view illustration of a sensor400 in accordance with an additional embodiment is shown. In anembodiment, the sensor components may be fabricated on a flexiblesubstrate 431. Since the substrate 431 is flexible, the sensor 400 maybe rolled into a tubular shape. This is particularly beneficial for gasconcentration sensing, because the sensor 400 can be easily insertedinto a gas line. That is, the sensor 400 may be disposed along theinterior surface of a gas line. Another implementation will be that allelectrodes are conformal to the inner surface of gas line tube but arefloated from the surface for better sensitivity. In addition, the sensorelectrodes can be directly fabricated on the inner surface of a solidcircular tube that is matched to the gas line.

In an embodiment, the sensor 400 may comprise a first line 412 _(A) anda second line 412 _(B). The first line 412 _(A) and the second line 412_(B) may be formed on opposite sides for the tubular sensor 400. In anembodiment, first fingers 414 _(A) may extend away from two differentsurfaces of the first line 412 _(A). For example, first fingers 414 _(A)may extend upwards and downwards from the first line 412 _(A).Similarly, second fingers 414 _(B) may extend away from two differentsurfaces of the second line 412 _(B). For example, second fingers 414_(B) may extend upwards and downwards from the second line 412 _(B). Inan embodiment, the first fingers 414 _(A) and the second fingers 414_(B) may be interdigitated with each other.

In some embodiments, the first line 412 _(A), the second line 412 _(B),the first fingers 414 _(A), and the second fingers 414 _(B) may besuspended up from the substrate 431 below the first line 412 _(A) andthe second line 412 _(B), similar to the embodiment shown in FIG. 4A. Insuch instances the gas may be flown over and below the capacitivestructures. As such, improved sensitivity is provided. Additionally,complications due to detecting a capacitance through the substrate 431are avoided.

In an embodiment, providing a tubular sensor 400 also allows for simplescaling of the sensor to improve the sensitivity. Particularly, morefingers 414 _(A) and 414 _(B) may be provided by extending the length(in the direction of the gas line) of the sensor 400. The length of thesensor 400 is only limited by the length of the gas line, and allows forsignificant scaling to provide enhanced sensitivities.

Referring now to FIG. 4C, a perspective view illustration of acapacitive sensor 400 is shown, in accordance with an embodiment. In anembodiment, the capacitive sensor 400 comprises a first electrode 410_(A) and a second electrode 410 _(B). In an embodiment, the firstelectrode 410 _(A) and the second electrode 410 _(B) may each comprise aplate 412 _(A) and 412 _(B). In an embodiment, first fingers 414 _(A)may extend out from the first plate 412 _(A), and second fingers 414_(B) may extend out from the second plate 412 _(B). The first fingers414 _(A) and the second fingers 414 _(B) may be plate like features.That is, the first fingers 414 _(A) and the second fingers 414 _(B) mayhave lengths and widths that are significantly larger than thicknessesof the first fingers 414 _(A) and the second fingers 414 _(B).

In an embodiment, the first fingers 414 _(A) and the second fingers 414_(B) may be interdigitated with each other. In an embodiment, the firstfingers 414 _(A) may extend out substantially perpendicular from thefirst plate 412 _(A), and the second fingers 414 _(B) may extend outsubstantially perpendicular from the second plate 412 _(B).

Referring now to FIG. 4D, a perspective view illustration of a sensor400 is shown, in accordance with an embodiment. In an embodiment, thesensor 400 may comprise a first electrode 410 _(A) and a secondelectrode 410 _(B). The first electrode 410 _(A) may comprise a firstplate 412 _(A) and a plurality of first pins 414 _(A). Similarly, thesecond electrode 410 _(B) may comprise a second plate 412 _(B) and aplurality of second pins 414 _(B). The first pins 414 _(A) and thesecond pins 414 _(B) may be disposed in an alternating pattern so thatfirst pins 414 _(A) are adjacent to second pins 414 _(B). In anembodiment, the pins 414 _(A) and 414 _(B) may extend out insubstantially perpendicular directions from the first plate 414 _(A) andthe second plate 414B.

In addition to different sensor architectures such as those shown inFIGS. 4A-4D, the sensitivity of the sensors may be enhanced throughvarious gas feed architectures. Examples of various gas feedarchitectures are shown in FIGS. 5A and 5B.

Referring now to FIG. 5A, a schematic of a gas feed architectures isshown, in accordance with an embodiment. The gas feed architecture maycomprise a gas line 540. A first end of the gas line 540 may beconnected to a gas source for providing an inert carrier gas, such asargon. An ampule 545 may be provided along the gas line 540. The ampule545 may provide a second gas to the gas line 540. For example, thesecond gas may be a precursor, such as TDMAT.

In an embodiment, the gas feed architecture may comprise a pair of gasconcentration sensors 500 _(A) and 500 _(B). The first gas concentrationsensor 500 _(A) may be before the ampule 545 and the second gasconcentration sensor 500 _(B) may be after the ampule 545. As shown,readings from the pair of gas concentrations sensors 500 _(A) and 500_(B) result in the equivalent circuit shown to the right of the gas feedarchitecture. A mathematical equation equivalent to the equivalentcircuit is V₀=V_(S)((C−C₀)/(C+C₀). As such, the differential capacitancebetween C−C₀ directly measures the gas concentration from the ampule. Inaddition, increases to the V_(S) voltage can be used to increase themeasured output V₀. That is, increases to V_(S) can be used to increasethe output signal dynamic range of the differential capacitive sensors500 _(A) and 500 _(B) to improve signal noise ratio (SNR). In addition,the differential configuration can suppress the common mode noise fromthermal, pressure, mechanical drifting noises etc.

Referring now to FIG. 5B, a schematic of a gas feed architecture isshown, in accordance with an additional embodiment. In an embodiment,the gas feed architecture comprises a first gas line 540 _(A) and asecond gas line 540 _(B). The first gas line 540 _(A) and the second gasline 540 _(B) may merge at a third gas line 540 _(C). In an embodiment,the first gas line 540 _(A) may supply a first portion of the gas intothe third gas line 540 _(C) and the second gas line 540 _(B) may supplya second portion of the gas into the third gas line 540 _(C). Forexample, the first gas line 540 _(A) may supply approximately 90% ormore of the gas fed into the third gas line 540 _(C), and the second gasline 540 _(B) may supply approximately 10% or less of the gas fed intothe third gas line 540 _(C). In a particular embodiment, the first gasline 540 _(A) may supply approximately 99% of the gas into the third gasline 540 _(C), and the second gas line 540 _(B) may supply approximately1% of the gas into the third gas line 540 _(C).

In an embodiment, the first gas line 540 _(A) may supply a first gas,such as an inert gas (e.g., argon), and the second gas line 540 _(B) maysupply a mixture of the first gas and a second gas, such as a precursor.For example, an ampule 545 along the second gas line 540 _(B) may supplythe second gas. Since the mixture in the second gas line 540 _(B) willsubsequently be diluted by the first gas in the first gas line 540 _(A),the percentage of the second gas in the second gas line 540 _(B) may berelatively large. For example, the second gas may account forapproximately 10% of the gas mixture in the second gas line. The largerconcentration of the second gas makes it easier to accurately measurethe concentrations with the sensor 500 _(B). For example, in anembodiment with a 99% gas flow in the first gas line 540 _(A) and a 10%concentration of the second gas in the second gas line 540 _(B), thefinal concentration in the third gas line 540 _(C) is approximately0.1%. As such, embodiments disclosed herein only need to be able tomeasure a gas concentration that is two orders of magnitude larger thanthe targeted gas concentration.

As noted above, the capacitance readings of the sensors may also beimpacted by temperature and pressure changes. Accordingly, someembodiments may include sensors that further comprise a temperaturesensor and/or a pressure sensor. Therefore, embodiments allow forchanges in temperature and pressure to be monitored for by the sensor.With the proper sensing algorithm, thermal and pressure parasiticeffects can be compensated by directly monitoring the temperature andpressure of gases to improve the monitoring accuracy as well assensitivity of gas concentration. Examples of such sensors are providedin FIGS. 6A and 6B.

Referring now to FIG. 6A, a cross-sectional illustration of a sensorsystem 680 is shown, in accordance with an embodiment. In an embodiment,the sensor system 680 comprises a sensor substrate 601. The sensorsubstrate 601 may be electrically and mechanically coupled to aprocessor 602, such as an ASIC or the like. For example, solder balls605 may be used to connect the sensor substrate 601 to the processor602.

The sensor system 680 may comprise a capacitive sensor 600, atemperature sensor 615, and a pressure sensor 617. The sensors 600, 615,and 617 may be electrically coupled to the solder balls 605 by throughsubstrate vias 606. In an embodiment, the capacitive sensor 600 may besubstantially similar to any of the capacitive sensors for gascompensation detection described in greater detail above. In anembodiment, the temperature sensor 615 may be a resistance temperaturedetector (RTD). For example, changes in a resistance across a conductivetrace 621 may be used to measure the change in temperature. Otherthermal sensors can also be integrated such as semiconductor junctionsensor, acoustic wave sensor, and thermistor, etc. The typicaltemperature sensing resolution can be 0.01 degree to 0.1 degree. Thetemperature range may be from room temperature to 650C. In anembodiment, the pressure sensor 617 may comprise a piezoelectric orcapacitive sensor. For example, a diaphragm 622 may span across a trench623 in the sensor substrate 601. The sensitivity for the pressure sensorcan range from a few millitorr (e.g., 10 mT) to 1 torr with the pressurerange from 10 Torr to 760 Torr. It is to be appreciated that temperaturesensors 615 and pressure sensors 617 similar to those shown in FIG. 6Amay be fabricated on the sensor substrate 601 using standardsemiconductor manufacturing processes. As such, integration of suchsensors can be implemented at a substantially low cost. However, it isto be appreciated that one or both of the temperature sensor 615 and thepressure sensor 617 may be provided as discrete components that areattached to the sensor substrate 601.

Referring now to FIG. 6B, a cross-sectional illustration of a sensorsystem 680 is shown, in accordance with an additional embodiment. Thesensor system 680 may be substantially similar to the sensor system 680in FIG. 6A, with the exception of the interconnect between the sensorsubstrate 601 and the processor 602. Instead of attaching the processor602 to the sensor substrate 601 by solder balls, interconnects such aswire bonds 603 are used. The use of wire bonds 603 allows for theprocessor 602 to be remote from the sensor substrate 601. For example,the sensor substrate 601 may be provided within a gas line and theprocessor 602 may be external to the gas line. Such embodiments areparticularly useful when the processing conditions (e.g., temperature)exceed the operating range of the processor 602. For example, the safeoperating maximum of the processor 602 may be approximately 150° C., andthe gas processing temperature may be above 150° C. As such, theoperating range of the sensor system 680 may be increased by removingthe processor 602 from the processing environment.

Referring now to FIG. 7, a cross-sectional illustration of asemiconductor processing tool 760 is shown, in accordance with anembodiment. In an embodiment, the semiconductor processing tool 760 is atool that includes the flow of one or more processing gasses 765 into achamber 761. For example, the semiconductor processing tool may comprisean atomic layer deposition (ALD) tool, a chemical vapor deposition (CVD)tool, a physical vapor deposition (PVD) tool, an etching tool, or anyother semiconductor processing tool that includes the flow of gas orgasses into the chamber 761.

The chamber 761 may be suitable for providing sub-atmospheric pressuresin order to process one or more substrates 763. For example, a vacuumpump (not shown) may be fluidically coupled to the chamber 761. In anembodiment, the substrate 763 may be supported on a pedestal 762 or thelike. The pedestal 762 may comprise a chucking mechanism (e.g.,electrostatic chucking, vacuum chucking, etc.). The pedestal 762 mayalso comprise heating and/or cooling functionality to control atemperature of the substrate 763.

In an embodiment, gas from a gas source 765 may flow into a gas line 740by passing through a valve 766. The gas source 765 may hold thesubstance in a gas phase or a liquid phase. In an embodiment, a gasconcentration sensor 700 may be integrated into the gas line 740. Thegas concentration sensor 700 may be similar to any of the gasconcentration sensors described in greater detail above. Particularly,in an embodiment, the gas concentration sensor 700 comprises a firstelectrode and a second electrode with interdigitated fingers to providea high capacitance value. Changes to the capacitance can be used todetermine the concentration of the gasses flowing through the gas line740. The gas line 740 may feed into a showerhead 764 for distributingthe gasses into the chamber 761. In an embodiment, the showerhead 764may also be suitable for generating a plasma in the chamber to enableplasma assisted processing operations (e.g., PE-ALD, PE-CVD, etc.).

In addition to measuring a gas concentration of a gas flowing into thechamber 761, embodiments may include placing the gas concentrationsensor 700 in various other locations of the processing tool 760. Forexample, the gas concentration sensor 700 may be used for detecting whena cleaning operation is completed. In such an embodiment, the gasconcentration sensor 700 may be placed inside process chamber near thevacuum port or in the exhaust line. The gas concentration sensor 700 maybe used to determine certain gas molecules or species in byproductsduring the cleaning, for example, when carbon is no longer present inthe byproducts. When the concentration of carbon goes below a giventhreshold, it can be determined that the cleaning of the chamber iscompleted.

In yet another embodiment, the gas concentration sensor 700 may be usedfor chamber condition monitoring. For example, a gas concentrationsensor 700 within the chamber 761 may be able to detect gasconcentrations that can be monitored for chamber health. Additionally,the gas concentration sensor 700 may be used to monitor de-absorption ofchemical species from the walls of the chamber 761. In yet anotherembodiment, the gas concentration sensor 700 may be integrated into anabatement system in order to monitor the disposal of processing gassesand byproducts from the processing tool 760.

Embodiments also include the use of a gas concentration sensor 700 indoping processes such as ion implantation. For example, a concentrationof the dopant gas can be determined in order to more accuratelydetermine a dopant concentration that will result on the substrate. Assuch, improved control of doping processes are enabled.

FIG. 8 illustrates a diagrammatic representation of a machine in theexemplary form of a computer system 800 within which a set ofinstructions, for causing the machine to perform any one or more of themethodologies described herein, may be executed. In alternativeembodiments, the machine may be connected (e.g., networked) to othermachines in a Local Area Network (LAN), an intranet, an extranet, or theInternet. The machine may operate in the capacity of a server or aclient machine in a client-server network environment, or as a peermachine in a peer-to-peer (or distributed) network environment. Themachine may be a personal computer (PC), a tablet PC, a set-top box(STB), a Personal Digital Assistant (PDA), a cellular telephone, a webappliance, a server, a network router, switch or bridge, or any machinecapable of executing a set of instructions (sequential or otherwise)that specify actions to be taken by that machine. Further, while only asingle machine is illustrated, the term “machine” shall also be taken toinclude any collection of machines (e.g., computers) that individuallyor jointly execute a set (or multiple sets) of instructions to performany one or more of the methodologies described herein.

The exemplary computer system 800 includes a processor 802, a mainmemory 804 (e.g., read-only memory (ROM), flash memory, dynamic randomaccess memory (DRAM) such as synchronous DRAM (SDRAM) or Rambus DRAM(RDRAM), etc.), a static memory 806 (e.g., flash memory, static randomaccess memory (SRAM), MRAM, etc.), and a secondary memory 818 (e.g., adata storage device), which communicate with each other via a bus 830.

Processor 802 represents one or more general-purpose processing devicessuch as a microprocessor, central processing unit, or the like. Moreparticularly, the processor 802 may be a complex instruction setcomputing (CISC) microprocessor, reduced instruction set computing(RISC) microprocessor, very long instruction word (VLIW) microprocessor,processor implementing other instruction sets, or processorsimplementing a combination of instruction sets. Processor 802 may alsobe one or more special-purpose processing devices such as an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA), a digital signal processor (DSP), network processor, or thelike. Processor 802 is configured to execute the processing logic 826for performing the operations described herein.

The computer system 800 may further include a network interface device808. The computer system 800 also may include a video display unit 810(e.g., a liquid crystal display (LCD), a light emitting diode display(LED), or a cathode ray tube (CRT)), an alphanumeric input device 812(e.g., a keyboard), a cursor control device 814 (e.g., a mouse), and asignal generation device 816 (e.g., a speaker).

The secondary memory 818 may include a machine-accessible storage medium(or more specifically a computer-readable storage medium) 832 on whichis stored one or more sets of instructions (e.g., software 822)embodying any one or more of the methodologies or functions describedherein. The software 822 may also reside, completely or at leastpartially, within the main memory 804 and/or within the processor 802during execution thereof by the computer system 800, the main memory 804and the processor 802 also constituting machine-readable storage media.The software 822 may further be transmitted or received over a network820 via the network interface device 808.

While the machine-accessible storage medium 832 is shown in an exemplaryembodiment to be a single medium, the term “machine-readable storagemedium” should be taken to include a single medium or multiple media(e.g., a centralized or distributed database, and/or associated cachesand servers) that store the one or more sets of instructions. The term“machine-readable storage medium” shall also be taken to include anymedium that is capable of storing or encoding a set of instructions forexecution by the machine and that cause the machine to perform any oneor more of the methodologies of the present disclosure. The term“machine-readable storage medium” shall accordingly be taken to include,but not be limited to, solid-state memories, and optical and magneticmedia.

In accordance with an embodiment of the present disclosure, amachine-accessible storage medium has instructions stored thereon whichcause a data processing system to perform a method of measuring the gasconcentration of a gas flown in a gas line using a capacitive gasconcentration sensor.

Thus, methods for measuring gas concentration have been disclosed.

What is claimed is:
 1. A gas concentration sensor, comprising: a firstelectrode, wherein the first electrode comprises first fingers; and asecond electrode, wherein the second electrode comprises second fingersthat are interdigitated with the first fingers.
 2. The gas concentrationsensor of claim 1, wherein the first electrode and the second electrodeare raised up from a substrate surface.
 3. The gas concentration sensorof claim 1, wherein the first electrode and the second electrode aredisposed on a flexible substrate.
 4. The gas concentration sensor ofclaim 3, wherein the flexible substrate is cylindrical, and wherein thefirst interdigitated fingers and the second interdigitated fingers curvealong the cylindrical shape of the flexible substrate.
 5. The gasconcentration sensor of claim 3, wherein the first electrode comprises afirst line, wherein the first fingers extend away from the first linefrom two surfaces of the first line, and wherein the second electrodecomprises a second line, wherein the second fingers extend away from thesecond line from two surfaces of the second line.
 6. The gasconcentration sensor of claim 1, wherein the first electrode comprises afirst pad, wherein the first fingers extend away from the first padperpendicular to the first pad, and wherein the second electrodecomprises a second pad, wherein the second fingers extend away from thesecond pad perpendicular to the second pad.
 7. The gas concentrationsensor of claim 6, wherein the first fingers and the second fingers areplates.
 8. The gas concentration sensor of claim 6, wherein the firstfingers and the second fingers are pins.
 9. The gas concentration sensorof claim 1, wherein the gas concentration sensor is provided in a gasfeed line of a semiconductor processing tool.
 10. The gas concentrationsensor of claim 1, further comprising: a temperature sensor; and apressure sensor.
 11. A semiconductor processing tool, comprising: achamber; a gas line for providing a source gas to the chamber; and a gasconcentration sensor in the gas line, wherein the gas concentrationsensor comprises: a first electrode, wherein the first electrodecomprises first fingers; and a second electrode, wherein the secondelectrode comprises second fingers that are interdigitated with thefirst fingers.
 12. The semiconductor processing tool of claim 11,wherein the first fingers and the second fingers are plates or pins. 13.The semiconductor processing tool of claim 11, wherein gas flows throughthe interdigitated first fingers and second fingers.
 14. Thesemiconductor processing tool of claim 11, wherein the semiconductorprocessing tool is an atomic layer deposition (ALD) tool.
 15. A gas feedarchitecture, comprising: a first gas line, wherein the first gas linereceives a first gas from a first gas source; an ampule along the firstgas line, wherein the ampule supplies a second gas to the first gasline; a first gas concentration sensor after the ampule, wherein thefirst gas concentration sensor comprises: a first electrode, wherein thefirst electrode comprises first fingers; and a second electrode, whereinthe second electrode comprises second fingers that are interdigitatedwith the first fingers.
 16. The gas feed architecture of claim 15,further comprising: a second gas sensor before the ampule.
 17. The gasfeed architecture of claim 15, further comprising: a second gas line,wherein the second gas line receives the first gas, and wherein thesecond gas line merges with the first gas line at a third gas line. 18.The gas feed architecture of claim 17, wherein the first gasconcentration sensor is between the ampule and the third gas line. 19.The gas feed architecture of claim 17, further comprising: a second gassensor on the second gas line.
 20. The gas feed architecture of claim19, wherein approximately 90% or more of gas flow into the third gasline is from the second gas line, or wherein approximately 1% or less ofgas flow into the third gas line is the second gas.